Physical Layer Security Enhancement via IRS Based on PD-NOMA and Cooperative Jamming

Intelligence reconfigurable surfaces (IRS) have attracted attention due to their ability to create an intelligent and controllable wireless propagation environment for supporting an efficient, and secure design. Security and privacy protection are fundamental requirements based on the eavesdropping attacks in wireless networks. Physical layer security (PLS) is an important technique that guarantees information-theoretic security regardless of the computational capability of eavesdropping. In addition, the non-orthogonal multiple access (NOMA) as a transmission technique supports higher spectral efficiency. With the aim of increasing the secrecy rate (SR) and providing a performance analysis of IRS-based NOMA physical layer security, we propose a practical scenario equipped with IRS-assisted NOMA, containing obstacles that cause no existing direct link between the base station (BS), users, and an eavesdropper. Despite the presence of obstacles between the IRS to the second user, the first user acts as an amplifier and forwarder (AF) relay for device-to-device (D2D) communication. An eavesdropper tracks the transmitting signals in two phases: IRS to the first user, and the first user to the second user. Therefore, the second user broadcast a cooperative jamming signal which is known for the first user. To analyze the proposed system model, we obtain a closed form for the ergodic secrecy rate that numerical results reveal that increasing the elements of the IRS can enhance it. Finally, we compare the performance of the orthogonal multiple access (OMA) and NOMA in the proposed system model, which that shows the NOMA can provide a 50% more ergodic secrecy rate compared to the OMA.